This invention relates to a numerical control method and, more particularly, to a numerical control method well-suited for application to a machine tool such as multi-spindle automatic lathe.
As shown in FIG. 1, a multi-spindle automatic lathe, which is for the purpose of shortening machining time and fostering mass production, has a number of mutually independently movable shafts (tools) TL.sub.1 through TL.sub.3 arrayed about a workpiece WK. The arrangement is such that the lathe subjects the workpiece WK to prescribed machining by applying machining performed by one tool followed by machining performed by a subsequent one of the tools when the preceeding machining is completed. However, in order to make it possible to control the movement of each tool independently in such a multi-spindle automatic lathe, a cam rotated by a rotary shaft, not shown, is provided for each and every tool, and it is arranged so that the workpiece is subjected to prescribed machining by moving the tools toward the workpiece independently due to rotation of the cams. This results in structural complexity and higher cost. Furthermore, though multi-spindle automatic lathes may be controlled numerically, the creation of NC data is troublesome.